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Abstract

We measured the absorption recovery times in reverse biased AlInGaAs multiple quantum well material designed to emit at around 1.5 μm wavelength. Absorption recovery times as low as 2.5ps were found at −4V bias, with values below 5ps consistently found for biases above 3V. The short absorption recovery times obtained under reverse bias were confirmed by using cross-absorption modulation in the material to demonstrate wavelength conversion of a 10GHz pulse train, showing both up and down conversion of the incident pulses.

Figures (3)

(a) Schematic diagram of the photocurrent detected pump-probe setup used to measure τa (b) Symbols show the measured absorption recovery times τa, as a function of the applied bias. The error bars represent the standard deviation of a number of measurements under the same conditions. The blue line shows the values of τa calculated using Eq. (1). (c) Typical trace of photocurrent versus delay line position. (d) The absorption recovery rate γa plotted on a log scale versus applied bias. The blue line shows the rate calculated using Eq. (1).

(a) Schematic diagram of the setup used for the wavelength conversion measurements. (b) (Top trace) λ ∼ 1550nm input pulses used for the experiment. This trace is not to scale and has been offset in the vertical direction for clarity. (Other traces) λ ∼ 1570nm output traces obtained from sample A under bias conditions from 0 to 3.5V, in 0.5V steps (from top to bottom) (c) The extinction ration and peak output powers obtained from sample B as a function of applied bias.

(a) The black curve shows values of the absorption recovery time τa obtained by fitting the wavelength converted signal to a single exponential function. The symbols denote different wavelengths used for the CW beam: ■ 1546.5nm, ● 1547.2nm, ▲ 1548.4nm, ♦ 1549.4nm. The blue open symbols and line show the values of τa measured from using the photocurrent detected pump-probe technique. The grey line shows values of τa reported by Nishimura et al. for InGaAsP MQWs [17]. The top axis shows electric field values calculated for the devices investigated in this work, and does not apply to the the Nishimura et al. data. (b) The measured FWHM of the wavelength converted pulses. Symbols have the same meaning as those in panel (a). (c) Reflection spectra of sample C measured under applied biases from 0V to 4V, at 1V intervals, showing the residual Fabry-Pérot resonances. The Stark shift of the absorption edge with increasing voltage can also be clearly seen.